Because of an increasing demand for a storage capacity and a data access rate of a magnetic disk storage device, the data access using a local area network (LAN) in a magnetic disk storage device environment is challenged in many aspects, including a limited network bandwidth, an access to massive data, etc. A technology of a LAN-free data access, i.e. a data access over a SAN, is widely popular.
The SAN is an optical fiber network, which is used in broad scope due to features of a fast data transmission rate, saving network resources in the LAN, etc. However, one main problem of the SAN is that although its internal data transmission rate is high, the SAN can not accomplish a file share in a heterogeneous environment. In the case that a plurality of entities require a shared access to same data in the SAN (typically, for example, in an application environment of a server-client mode, a server and a client need a shared access to data), the SAN can only be applied to a magnetic tape storage device environment, rather than a magnetic disk storage device environment, for which the reason is that a large number of logic volumes are independent devices for a storage server and a client in the magnetic disk storage device environment, and a device description file of a logic volume identified by the server is different from a device description file of the same one identified by the client. However, since a magnetic tape belongs to a sequential storage medium, its access efficiency is low. Sometimes, it will take a long time to find a file in sequence. Therefore, there is a need for a technical solution that a data transmission is implemented between a user and a storage device using the SAN in the magnetic disk storage environment. For example, such a typical demand is that when an operation of a data de-duplication is performed, it is necessary to divide a file into small file blocks, and the small file blocks may be dispersed on different volumes. That is, in order to obtain one file, it is possibly required to access a plurality of volumes to get a plurality of small file blocks dispersed on the plurality of volumes, which is easily achieved in the magnetic disk storage environment, but in the magnetic tape storage environment, it is required to search the small file blocks on a plurality of magnetic tapes in sequence, consuming a long time and a lot of magnetic tape hardware resources. If an operation of a data de-duplication is performed in the magnetic disk storage environment connected by the SAN, a working efficiency can be greatly improved.
In the prior art, there exists the following two technical solutions solving the above problem. One solution is to first let a user access data on a magnetic tape storage device over the SAN, and then migrate the data in the magnetic tape storage device to a magnetic disk storage device. In fact, the method is equivalent to using a magnetic tape device as a temporary storage medium with a defect that a large number of hardware consumptions are caused and additional data migration time to migrate the data on the magnetic tape to the magnetic disk is required. The other solution is to utilize a distributed file system (e.g. a GPFS) so that both a server and a user can access data on the magnetic disk over the SAN. However, such solution has a defect that the distributed file system costs are very expensive, and even far more expensive than the magnetic disk storage device itself. Thus, many medium and small-sized enterprise users would not like to choose the distributed file system.